This invention relates to an internal combustion engine and more particularly to an improved induction system for such an engine having improve performance particularly at low and mid range speeds without adversely affecting high speed performance.
It is well known that the induction system for an engine is a compromise between the obtaining of maximum performance and good running and fuel consumption at low speeds. It has also been proposed to provide an induction system induces turbulence in the combustion chamber in the form of swirl or tumble to improve low speed running and particularly to permit lean combustion. Examples of this are shown in U.S. Pat. No. 5,671,712 and Japanese Published Application 05-026135.
In the noted the United States Patent, the induction system includes a control valve which controls the flow of air to three intake valves provided for each combustion chamber. At low speeds, the control valve is operated so that the flow is directed through a restricted passageway toward one of the side intake valves. This also directs the flow into the combustion chamber in a direction of the to improve tumble and/or swirl. However, the flow also tends to go toward the other intake valves and diminishes the overall effect.
In the Japanese publication, on the other hand, the intake system cooperates with two intake valves and is designed so as to promote an increased flow to one of the intake valves by restricting the flow area. This will generate some turbulence. However, the arrangement restricts the overall ability of the engine to breath and thus reduces high speed performance.
In addition to the noted problems, in each approach in addition to the higher velocity flow through the restricted passage there is still a slower flow through the remainder of the valve opening through which the restricted opening passes. Thus even this added turbulence is reduced.
It is therefor a principal object to this invention to provide an induction system for an engine that will produce turbulence when desired and the desired flow directions without restricting maximum power output. In addition when the turbulence is generated this is done in such a way as to maintain the air flow in the direction or directions desired in the combustion chamber without dissipation of the effect.